It is known to use urethane polyumers in the repair of bumpers and like synthetic organic polymer body components, although such use is far less than use of epoxy and other curable resins than urethane. Known urethanes, however, are not as hard as desired. The chemistry of the urethane polymer is such that attempting to make a harder polymer requires relatively higher amounts of isocyanate reagent. In the auto repair situation, however, relatively higher amounts of isocyanate are desirably avoided since cure times to a sandable stage are increased, necessitating delays in finishing the repair, the painting and so on and increasing labor costs. Thus presently known urethanes have been limited in hardness so as to get fast sandability. An important factor in determining utility of polymer compositions for auto body repair is the rapidity with which the composition reaches a sandable condition and the ability of the polymer composition to sand in extremely thin sections, near the edge of a patch for example where the material is nearly feathered. Other properties such as hardness, shelf life, broad tolerance for mixing variations, adhesion to the substrate, colorability, ease of application and clean up and reproducibility from batch to batch, together with convenient packaging for efficient use are other criteria of value in assessing bumper repair compositions. Heretofore available compositions have been lacking some or all of these qualities to some degree, but the present composition affords them all and is a breakthrough in the art and science of urethane compositions which are adhesive, sandable, rapid curing, tough, and capable of providing predictable reproducibility in use after use.